1. Field of the Invention
The invention relates to a device in a printing machine with an application head for applying glue in a line to a printing web.
2. Description of the Related Art
European reference EP 0 486 812 A2 discloses a device for applying a liquid to a substrate (printing web) in a printing machine. The application head described in that document applies a liquid, which is preferably glue, in the form of lines to a substrate, particularly to a paper web entering a folding device. It may happen, as the liquid is processed, that the liquid is not applied exactly along the desired line, but rather at a distance therefrom. This reference describes a device to check whether the liquid is applied exactly along the preestablished line or not; in the event of deviation, a defined repositioning of the application head is permitted.
In the known device, pigments are added to the application liquid, by means of which the liquid already applied to the substrate can be detected using special visualization means. As a result, the position of the lines of applied liquid can be measured. To readjust the application head applying this liquid, the applied liquid is made visible, the distance between the line formed by the applied liquid and the desired position is measured and, in the event of deviation, the associated application head is adjusted.